(a) Field of the Invention
The present invention relates to a backlight driving apparatus of a liquid crystal display, and more in particular to a circuit capable of preventing an arc of an inverter of the backlight.
(b) Description of the Related Art
Display devices used for monitors of computers and television sets include self-emitting displays such as light emitting diodes (LEDs), electroluminescences (ELs), vacuum fluorescent displays (VFDs), field emission displays (FEDs) and plasma panel displays (PDPs) and non-emitting displays such liquid crystal displays (LCDs) requiring light source.
An LCD includes two panels provided with field-generating electrodes and a liquid crystal (LC) layer with dielectric anisotropy interposed therebetween. The field-generating electrodes supplied with electric voltages generate electric field in the liquid crystal layer, and the transmittance of light passing through the panels varies depending on the strength of the applied field, which can be controlled by the applied voltages. Accordingly, desired images are obtained by adjusting the applied voltages.
The light may be emitted from a light source equipped in the LCD or may be natural light. When using the equipped light source, the total brightness of the LCD screen is usually adjusted by regulating the ratio of on and off times of the light source or regulating the current through the light source.
A light device for an LCD, i.e., a backlight unit usually includes a light source and an inverter for driving the light source. The light source includes a plurality of fluorescent lamps and the inverter converts a DC (direct current) input voltage from an external device into an AC (alternating current) voltage, and then applies the voltage to turn on the lamps.
For obtaining good image quality, the current flowing in the lamps is required to be uniform such that the luminescence of the lamps uniform. In order to obtain uniform current, a current detector for detecting the current in the lamps is provided and the current is feedback-controlled depending on the detected current.
A conventional technique senses a feedback current and shuts down an inverter when there is no detected current due to change of loads such as disconnection of lamps or separation of an output connector, etc. However, there are some cases that the feedback current is detected even though abnormal operation occurs. For example, the disconnection in a transformer, loose connection of the output connector and so on may generate arcs, which in turn generate the feedback current. Since the inverter is not shut down in this condition, the arc generation continues to burn the transformer or the output connector.